Insights into the hierarchical structure and digestion rate of alkali-modulated starches with different amylose contents

Combined analytical techniques were used to explore the effects of alkali treatment on the multi-scale structure and digestion behavior of starches with different amylose/amylopectin ratios. Alkali treatment disrupted the amorphous matrix, and partial lamellae and crystallites, which weakened starch molecular packing and eventually enhanced the susceptibility of starch to alkali. Stronger alkali treatment (0.5% w/w) made this effect more prominent and even transformed the dual-phase digestion of starch into a triple-phase pattern. Compared with high-amylose starch, regular maize starch, which possesses some unique structure characteristics typically as pores and crystallite weak points, showed evident changes of hierarchical structure and in digestion rate. Thus, alkali treatment has been demonstrated as a simple method to modulate starch hierarchical structure and thus to realize the rational development of starch-based food products with desired digestibility

PLA/WOOD BIOCOMPOSITES: IMPROVING COMPOSITE STRENGTH BY CHEMICAL TREATMENT OF THE FIBERS

A resol type phenolic resin was prepared for the impregnation of wood particles used for the reinforcement of PLA. A preliminary study showed that the resin penetrates wood with rates depending on the concentration of the solution and on temperature. Treatment with a solution of 1 wt% resin resulted in a considerable increase of composite strength and decrease of water absorption. Composite strength improved as a result of increased inherent strength of the wood, but interfacial adhesion might be modified as well. When wood was treated with resin solutions of larger concentrations, the strength of the composites decreased, first slightly, then drastically to a very small value. A larger amount of resin results in a thick coating on wood with inferior mechanical properties. At large resin contents the mechanism of deformation changes; the thick coating breaks very easily leading to the catastrophic failure of the composites at very small loads

Biocomposite from polylactic acid and lignocellulosic fibers: structure-property correlations

ABSTRACT PLA biocomposites were prepared using three corncob fractions and a wood fiber as reference. The composites were characterized by tensile testing, scanning electron (SEM) and polarization optical (POM) microscopy. Micromechanical deformation processes were followed by acoustic emission measurements. The different strength of the components was proved by direct measurements. Two consecutive micromechanical deformation processes were detected in composites containing the heavy fraction of corncob, which were assigned to the fracture of soft and hard particles, respectively. The fracture of soft particles does not result in the failure of the composites that is initi-ated either by the fracture of hard particles or by matrix cracking. Very large particles debond easily from the matrix resulting in catastrophic failure at very low stresses. At sufficiently large shear stresses large particles break easily during compounding, thus reinforcement depending on interfacial adhesion was practically the same in all composites irrespectively of initial fiber characteristics

Fiber association and network formation in PLA/lignocellulosic fiber composites.

PLA composites were prepared in an internal mixer with a lignocellulosic fiber having relatively large aspect ratio. Fiber content changed between 0 and 60 vol% and the homogenized material was compression molded to 1 mm thick plates. The composites showed anomalous behavior above certain fiber content. Their modulus and especially their strength decreased drastically and modeling also proved the loss of reinforcement at large fiber contents. Micromechanical testing showed that the mechanism of deformation and failure changes at a critical fiber content. Microscopic analysis indi-cated the formation of a network purely from geometrical reasons. The inherent strength of the network is very small because of the weak forces acting among the fibers. This weak inherent strength makes the structure of the composites very sensitive to pro-cessing conditions, and decreases strength, reproducibility as well as reliability

Development and characterization of green composites from bio-based polyethylene and peanut shell

This is the accepted version of the following article: Garcia-Garcia, D., Carbonell-Verdu, A., Jordá-Vilaplana, A., Balart, R. and Garcia-Sanoguera, D. (2016), Development and characterization of green composites from bio-based polyethylene and peanut shell. J. Appl. Polym. Sci. 43940 doi: 10.1002/app.43940, which has been published in final form at http://dx.doi.org/10.1002/app.43940[EN] In the present work, different compatibilizers, namely polyethylene-graft-maleic anhydride (PE-g-MA), polypropylene-graftmaleic anhydride (PP-g-MA), and polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleic anhydride (SEBS-g-MA) were used on green composites derived from biobased polyethylene and peanut shell (PNS) flour to improve particle polymer interaction. Composites of high-density polyethylene/peanut shell powder (HDPE/PNS) with 10 wt % PNS flour were compatibilized with 3 wt % of the abovementioned compatibilizers. As per the results, PP-g-MA copolymer lead to best optimized properties as evidenced by mechanical characterization. In addition, best particle matrix interface interactions with PP-g-MA were observed by scanning electron microscopy (SEM). Subsequently HDPE/PNS composites with varying PNS flour content in the 5 30 wt % range with PP-g-MA compatibilizer were obtained by melt extrusion and compounding followed by injection molding and were characterized by mechanical, thermal, and morphological techniques. The results showed that PNS powder, leads to an increase in mechanical resistant properties (mainly, flexural modulus, and strength) while a decrease in mechanical ductile properties, that is, elongation at break and impact absorbed energy is observed with increasing PNS flour content. Furthermore, PNS flour provides an increase in thermal stability due to the natural antioxidant properties of PNS. In particular, composites containing 30 wt % PNS powder present a flexural strength 24% and a flexural modulus 72% higher than the unfilled polyethylene and the thermo-oxidative onset degradation temperature is increased from 232 8C up to 2548C thus indicating a marked thermal stabilization effect. Resultant composites can show a great deal of potential as base materials for wood plastic composites.This research was supported by the Ministry of Economy and Competitiveness -MINECO, Ref: MAT2014-59242-C2-1-R. Authors also thank to "Conselleria d'Educacio, Cultura i Esport" - Generalitat Valenciana, Ref: GV/2014/008 for financial support. A. Carbonell-Verdu wants to thank Universitat Politecnica de Valencia for financial support through an FPI grant. D. Garcia-Garcia wants to thanks the Spanish Ministry of Education, Culture and Sports for the financial support through an FPU grant (FPU13/06011).García García, D.; Carbonell Verdú, A.; Jorda-Vilaplana, A.; Balart Gimeno, RA.; García Sanoguera, D. (2016). Development and characterization of green composites from bio-based polyethylene and peanut shell. Journal of Applied Polymer Science. 133(37):1-12. https://doi.org/10.1002/APP.43940S1121333

Manufacturing and properties of biobased thermoplastic composites from poly(lactid acid) and hazelnut shell wastes

This is the peer reviewed version of the following article: Balart, J.F., Garcia-Sanoguera, David, Balart, Rafael, Boronat, Teodomiro, Sanchez-Nacher, Lourdes. (2018). Manufacturing and properties of biobased thermoplastic composites from poly(lactid acid) and hazelnut shell wastes.Polymer Composites, 39, 3, 848-857. DOI: 10.1002/pc.24007 , which has been published in final form at [Link to final article using the DOI]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.[EN] Poly(lactic acid), PLA-based green composites were obtained with hazelnut shell flour (HSF) derived from the food industry thus leading to fully biodegradable materials with attracting properties. The hazelnut shell flour content varied in the 10-40wt% range. An increase in the degree of crystallinity with increasing HSF was detected, mainly due to the nucleating effect of lignocellulosic particles. The thermodimensional stability was noticeably improved with increasing HSF amount as evidenced by a remarkable decrease in the coefficient of thermal-linear expansion. Increasing HSF leads to stiffer materials as HSF particles act as interlock points that restrict polymer chain motion. Addition of hazelnut shell flour as filler in PLA-based green composites leads to fully biodegradable composites with balanced mechanical and thermal properties. Furthermore, it gives a solution to upgrade wastes from the hazelnut industry and contributes to lower the cost of PLA-based materials. POLYM. COMPOS., 39:848-857, 2018. (c) 2016 Society of Plastics EngineersContract grant sponsor: Ministerio de Economia y Competitividad-MINECO; contract grant number: MAT2014-59242-C2-1-R; contract grant sponsor: Conselleria d'Educacio, Cultura i Esport; contract grant number: GV/2014/008.Balart, J.; Garcia-Sanoguera, D.; Balart, R.; Boronat, T.; Sanchez-Nacher, L. (2018). Manufacturing and properties of biobased thermoplastic composites from poly(lactid acid) and hazelnut shell wastes. Polymer Composites. 39(3):848-857. doi:10.1002/pc.24007S84885739

PLA/Lignocellulosic fiber composites: particle characteristics, interfacial adhesion and failure mechanism.

PLA composites were prepared using six lignocellulosic fibers with widely varying particle characteristics. The composites were characterized by tensile testing, scanning electron (SEM) and polarization optical (POM) microscopy. Micromechanical deformation processes during loading were followed by acoustic emission measurements. Interfacial adhesion was estimated by three independent methods. Contrary to most claims published in the literature, interfacial adhesion between PLA and natural fibers was found to be rather strong, a result confirmed by the quantitative estimation of adhesion strength, acoustic emission measurements and SEM study. Strong interfacial adhesion results in weak dependence of the extent of reinforcement on the particle characteristics of the reinforcing fibers. Both acoustic emission measurements and microscopy indicated that the dominating micromechanical deformation process is the fracture of the fibers and close correlation was found between the initiation stress of fiber fracture, reinforcement and the ultimate strength of the composites

Biocomposites of different lignocellulosic wastes for sustainable food packaging applications

The suitability of three local lignocellulosic wastes i.e. almond shell (AS), rice husk (RH) and seagrass (SG) as fillers in PHB/Fiber composites applications has been studied. PHB/Fiber composites with 10 phr and 20 phr fiber content were prepared by melt blending. The influence of the fiber type (size, morphology and origin) and content on the morphological, mechanical and thermal properties of the as obtained composites has been assessed. To evaluate the potential use in food packaging applications, the barrier performance to water, thermoforming ability and disintegration in controlled composting conditions of the composites were also studied. All the fibers have demonstrated to be apt for their use as fillers in PHB/Fiber composites, showing a reinforcing effect without affecting the crystallinity and the disintegration rate of PHB. The thermal stability and the water barrier performance of the composites were reduced by the presence of the fibers. Nevertheless, the addition of AS resulted in the best balance of properties, in terms of permeability and mechanical properties, finding an enhancement of the thermoforming ability of PHB when 10 phr of AS was added